// 导出页面为PDF格式
import html2Canvas from 'html2canvas'
import JsPDF from 'jspdf'
import { Loading } from 'element-ui'
let loading

export default class PadDownloader {
  static install(Vue, options) {
    Vue.prototype.downloadPdf = function(options) {
      loading = Loading.service({
        lock: true,
        text: '正在下载文件...',
        background: 'rgba(0,0,0,.5)'
      })
      const title = options.title
      const content = document.querySelector('#' + options.selector)
      html2Canvas(content, {
        allowTaint: true,
        useCORS: true
      }).then(function(canvas) {
        const contentWidth = canvas.width
        const contentHeight = canvas.height
        const pageHeight = contentWidth / 592.28 * 841.89
        let leftHeight = contentHeight
        let position = 0
        const imgWidth = 595.28
        const imgHeight = 592.28 / contentWidth * contentHeight
        const pageData = canvas.toDataURL('image/jpeg', 1.0)
        const PDF = new JsPDF('', 'pt', 'a4')
        if (leftHeight < pageHeight) {
          PDF.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight)
        } else {
          while (leftHeight > 0) {
            PDF.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)
            leftHeight -= pageHeight
            position -= 841.89
            if (leftHeight > 0) {
              PDF.addPage()
            }
          }
        }
        loading.close()
        PDF.save(title + '.pdf')
      })
    }
  }
}
